The board has a complicated DMA architecture. The Discovery system controller is connected to the Rm9000 processor over the SysAD bus. The Discovery controller cannot be a master on this bus. Hence, the Discovery IO devices can __only__ DMA data to the Discovery memory (128 MB). If the board is configured to use 384 MB memory, then the Rm9000 256 MB memory cannot be used by the Discovery controller. The board can operate in the following configurations:

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The board has a complicated DMA architecture. The Discovery system controller is connected to the Rm9000 processor over the SysAD bus. The Discovery controller cannot be a master on this bus. Hence, the Discovery IO devices can ''only'' DMA data to the Discovery memory (128 MB). If the board is configured to use 384 MB memory, then the Rm9000 256 MB memory cannot be used by the Discovery controller. The board can operate in the following configurations:

1. 128 MB memory. Use the Discovery memory

1. 128 MB memory. Use the Discovery memory

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2. 384 MB memory. DMA data in the 128 MB Discovery memory has to be moved to the 256 MB Rm9000 memory and vice-versa. One of the methods used in 2.4 Linux was configuring the 128 MB memory as CONFIG_ISA

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2. 384 MB memory. DMA data in the 128 MB Discovery memory has to be moved to the 256 MB Rm9000 memory and vice-versa. One of the methods used in 2.4 Linux was putting the entire dmable memory into [[Memory_zones|ZONE_DMA]] but this did require modification of many drivers and I/O subsubsystems so wasn't really acceptable.

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3. All Rm9000 memory configured as CONFIG_HIGHMEM.

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3. All Rm9000 memory configured as [[Highmem|highmem]. This is the solution used in Linux 2.6. It's the preferable way of doing things because it's consistant with the published internal Linux APIs and doesn't require extensive modifcations.

Revision as of 18:55, 4 November 2004

Contents

General Information

Momentum Jaguar ATX board has a Rm9000 processor (internal name Gemini) . This can be single core or dual core. The board has a Marvell Discovery II (MV64340) system controller. Newer versions of the board have a Marvell Discovery III (MV64440) system controller. This new board is called Jaguar-3.

This board is supported in Linux 2.4 and 2.6 versions (32-bit and 64-bit). The Hypertransport interface is compatible with Alliance Natasha/Sipacket HT-PCIX bridge and the PLX HT-PCIX bridge

Board Limitations

The board has a complicated DMA architecture. The Discovery system controller is connected to the Rm9000 processor over the SysAD bus. The Discovery controller cannot be a master on this bus. Hence, the Discovery IO devices can only DMA data to the Discovery memory (128 MB). If the board is configured to use 384 MB memory, then the Rm9000 256 MB memory cannot be used by the Discovery controller. The board can operate in the following configurations:

1. 128 MB memory. Use the Discovery memory

2. 384 MB memory. DMA data in the 128 MB Discovery memory has to be moved to the 256 MB Rm9000 memory and vice-versa. One of the methods used in 2.4 Linux was putting the entire dmable memory into ZONE_DMA but this did require modification of many drivers and I/O subsubsystems so wasn't really acceptable.

3. All Rm9000 memory configured as [[Highmem|highmem]. This is the solution used in Linux 2.6. It's the preferable way of doing things because it's consistant with the published internal Linux APIs and doesn't require extensive modifcations.